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Debate kit Grade 8 Science

Removing Alderfen Dam to Restore Fish Passage: A Grade 8 Debate Kit

A grade 8 debate kit on removing a fictional aging dam to restore fish migration, weighing real dissolved-oxygen science against hydropower and cost.

Objectives

  1. Students will evaluate evidence on both sides of a dam-removal resolution involving ecological and infrastructure tradeoffs.
  2. Students will construct and deliver a rebuttal supported by named evidence from the Evidence File.
  3. Students will apply a real dissolved-oxygen benchmark to evaluate a claim about reservoir water quality.

Vocabulary

Hydropower
Electricity made from moving water, usually water falling through a dam. It is a renewable power source that can start up quickly when the electric grid needs it.
Reservoir
A human-made lake, usually created by a dam, that stores water for later. Reservoirs supply cities and farms and help control floods.
Dissolved oxygen
Dissolved oxygen is the oxygen gas mixed into water that fish and other underwater animals breathe. Cold, moving water holds more oxygen than warm, still water.

Also: fish passage

Teacher overview

This is a two-team structured debate spanning two class sessions totaling about 60 minutes, with prep time built into a shorter first session before the debate itself runs in a second session. Students argue for or against removing a fictional small hydroelectric dam to restore fish passage on a fictional river, a resolution with genuine tension between ecological restoration and the practical benefits a dam provides. A common misconception students bring to dam debates is assuming a dam is either entirely good or entirely bad; the Evidence File below is built to show that both removing and keeping Alderfen Dam carry real trade-offs a town must weigh.

Removing Alderfen Dam to Restore Fish Passage: A Grade 8 Debate Kit — Grade 8 Science
Name: ____________________________ Date: ______________

Resolution & Background

Resolution: "The town of Alderfen should remove the aging Alderfen Dam to restore fish passage on the Sable River, even though this would end the dam's small hydropower supply."

Background: Alderfen Dam is a fictional dam made for this debate. It has stood on the fictional Sable River since the 1950s. The dam makes a small amount of hydropower for the town. It also blocks fish, such as salmon and shad, from swimming upstream. Biologists say the dam blocks about 40 miles of fish habitat. Old dams can also cause water-quality problems. Water behind a dam warms in the summer sun, and warm water holds less oxygen. In the reservoir's deep, still water, decay can also use up oxygen that is not replaced. Either way, dissolved oxygen can drop below 5 mg/L, the level most fish need to live. Removing dams has become a common way to restore rivers. But every dam gives a town something it values, such as power, flood control, water supply, or recreation. A town must weigh those benefits against the gains from removing a dam.

Evidence File

Case for removing the dam:

  1. Alderfen Dam blocks about 40 miles of fish habitat upstream. This is a made-up estimate for this debate. Fish on other rivers have come back strongly once dams there let them pass again.
  2. Water behind old dams like Alderfen's can warm up and sit still. This can push dissolved oxygen below 5 mg/L, the level most fish need to live. This is a real water-quality mark used across the country. (Source: standard water-quality benchmark, EPA/USGS.)
  3. A made-up local group for this debate, the Sable River Anglers Coalition, says dam removal would bring back fishing and fun the town lost long ago. This could bring visitors and money back to Alderfen's riverfront shops.
  4. Alderfen Dam makes only a small amount of power. For scale, Hoover Dam is one of the biggest hydropower dams in the country. It is built to make about 2,080 megawatts at full capacity, though years of drought and low water in Lake Mead have cut the power it actually makes by about 30 percent. Alderfen's own dam makes only a small piece of that. (Source: US Bureau of Reclamation, for the Hoover Dam numbers only. Alderfen Dam's own output is made up for this debate.)

Case against removing the dam:

  1. Even a small dam like Alderfen's gives clean, local power without burning fuel. Removing it means finding power from another source. That source has its own costs and environmental effects.
  2. A made-up report from an Alderfen town engineer, written for this debate, says removing the dam and fixing the riverbank would cost several million dollars. The town would need to weigh that cost against its other needs.
  3. The reservoir behind Alderfen Dam has given the town's parks and a small marina steady water for decades. Removing the dam would end that calm water. It would change how people use the riverfront.
  4. A made-up Alderfen public works spokesperson, written for this debate, says a fish ladder or bypass channel could let fish pass while keeping the dam and its power. The town has not yet studied this option closely.

From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.

Rubric
Criterion Emerging Developing Proficient Advanced
Evidence use Repeats a claim about the dam with no cited evidence Cites one piece of evidence from the Evidence File without explaining its relevance Cites at least two pieces of evidence and explains how each supports the team's position on the resolution Cites multiple pieces of evidence, explains their relevance, and anticipates the opposing side's likely response
Rebuttal quality Does not respond to the opposing team's points Responds to an opposing point but without new evidence Directly rebuts a specific opposing point using evidence from the file Rebuts multiple opposing points and explains why the team's evidence outweighs them
Organization & delivery Argument is difficult to follow, with no clear structure Argument has a structure but transitions between points are unclear Argument follows a clear claim-evidence-conclusion structure throughout Argument is clearly structured, confidently delivered, and directly responsive to the resolution

Differentiation

Support (below grade level)

Provide each side with a simplified evidence card listing only its two strongest points from the Evidence File, and give sentence starters for rebuttals, such as "Our opponents claim ___, but the evidence shows ___."

Extension (above grade level)

Ask students to reread the fish ladder or bypass channel option in the "against" case, using only the Evidence File and not outside sources, and incorporate that alternative into a stronger rebuttal for either side.

ELL supports

Pre-teach "hydropower," "fish passage," "reservoir," and "dissolved oxygen" with simple definitions and a labeled diagram of a dam showing the reservoir, the fish-blocking structure, and the river continuing downstream. Allow students to deliver rebuttals from written notes rather than extemporaneously.

Extensions

Have students research, with teacher guidance, a real dam-removal project in the United States and compare its stated reasons and outcomes to the fictional Alderfen Dam case debated in class.